Vidalia isn't included anymore in the Tor Browser Bundle.
But you don't really need Vidalia for this workaround.
As I could see in the HowTo everything you have to do is edit the torrc.
So that you are using Tor on Windows 7 the torrc lies under:
Just open it in notepad or something similar and add the following line:
Save it and restart your Tor Browser Bundle.
You now have configured your Tor to only exit over Great Britain nodes without needing Vidalia :)
Also I hope you are aware of the fact that the Tor network might be too slow for the iPlayer. So you or (more likely) the iPlayer has to buffer sometimes.
It also wouldn't be good for the whole network as this player needs a lot of bandwidth.
Setting up a VPN in GB would be a better and more stable solution for this.